A key is given for the separation of the species of the genus Hydalicus Leach found in Fennoscandia. Diagnostic characters are discussed and illustrations of the male genitalia are provided. The nomenclature of the European species of the subgenus Hydalicus s. str. is discussed and a check list is given. Hydalicus moestus Sharp and H. laevipennis Thomson are considered synonyms of H. aruspex Clark.